1. Field of the Invention
The present invention relates to a cartridge-type mechanical seal. More specifically, this invention relates to the cartridge-type mechanical seal constituted in such a way that a stationary seal unit and a rotary unit seal unit are coupled and locked by a plurality of setting spacers when the seal is not installed. The stationary seal unit is to be fixed to the shaft seal casing of rotary equipment and the rotary seal unit that can be installed or removed in simple procedures is to be mounted on the rotary shaft extending through the shaft seal casing.
2. Description of the Prior Art
Generally, mechanical seals are made up of a stationary seal unit fixed to the shaft seal casing of rotary equipment and a rotary seal unit mounted on the rotary shaft that extends through the shaft seal casing. The mounting of the mechanical seal on the shaft seal casing and rotary shaft involves putting in place a number of such individual component parts as the seal rings one by one in a specific procedure.
Meanwhile, the positional relation between the component parts making up the seal units is an important factor determining the performance of the mechanical seal. The individual component parts have to be installed so that the positional relation is properly established. That is, those component parts have to be assembled with care taken to meet a number of requirements. The requirements include proper positioning of the two seal units in the axial and radial directions and securing parallelism and concentricity between the opposed seal end faces of the stationary seal ring and the rotary seal ring. It is understood that the parallelism is the perpendicularity to the axis of the shaft.
But, since those seal units are made up of a large number of component parts, the mounting of them on rotary equipment in a proper manner is quite difficult to even skilled mechanics, much more so to unskilled workers. The mechanical seal does not sometimes work properly because of faulty installation. The maintenance including removal from and re-installation on the rotary equipment is a troublesome and difficult job.
It is an object of the present invention to provide a cartridge-type mechanical seal wherein the seal units can be assembled with ease and accuracy into an integral structure (cartridge structure) in the same form as that of a mechanical seal put in service and wherein the mechanical seal in the assembled form can be directly installed on or removed from rotary equipment, thus making it possible and easy for a mechanic to perform maintenance involving installation and removal of the assembly from rotary equipment in a proper manner without difficulty.
It is another object of the present invention to provide a cartridge-type mechanical seal in which the stopper ring can be mounted on the stopper ring sleeve easily and securely such that common use of setting spacers, whose number is freely chosen, and simplification and mass production of the setting spacers, are permitted.
It is still another object of the present invention to provide a cartridge-type mechanical seal that can be reduced in size and weight. That is, the sleeve can now be made thin in wall thickness to the maximum extent, and therefore the stationary seal ring through which the sleeve is inserted can be reduced in diameter to the maximum extent. That in turn makes it possible to reduce the component parts of the seal units and the mechanical seal itself in size and weight.
It is a still further object of the present invention to provide a cartridge-type mechanical seal applicable, without changing the construction, to the shaft seal area of rotary equipment that is not designed for use of the mechanical seal (for instance stuffing boxes that are designed for a gland packing) because the mechanical seal can be mounted on and removed from the rotary unit in the assembled state identical to the form in service. Hence, the mechanical seal can easily deal with the changes in sealing conditions and required sealing performance, thus permitting its wide use and raising the practical value.
It is a further object of the present invention to provide a cartridge-type mechanical seal that is simple in construction and low in manufacturing costs and, in addition, is easy to assemble. That is, a means for thrusting the stationary seal ring and means for preventing that ring from rotating are simplified to the maximum extent. Further, the number of the component parts for those means is reduced. That simplifies the construction and reduces the manufacturing costs.
Those objects of the present invention are attained by providing cartridge-type mechanical seal so constructed that a stationary seal unit and a rotary unit seal unit are coupled, using a plurality of setting spacers in the same relative relations in position in the axial and radial directions as when the mechanical seal is in service. The stationary seal unit is to be fixed to the shaft seal casing of rotary equipment and the rotary seal unit that can be installed and removed in a simple procedure is to be mounted on the rotary shaft extending through the shaft seal casing. Those setting spacers are removable after the two seal units are installed on the shaft seal casing and the rotary shaft.
In a preferred embodiment, the stationary seal unit has a cylindrical mounting case to be installed on the shaft seal casing, a stationary seal ring held within the mounting case and a circular positioning surface formed on the mounting case concentrically with the stationary seal ring. The rotary seal unit has a sleeve, that is, a thin wall cylinder which can be mounted around and removed from the rotary shaft and which is placed concentrically in the stationary seal unit with one end of the sleeve protruding from the mounting case, a rotary seal ring installed, opposite to the stationary seal ring, at the other end of the sleeve, a stopper ring which is mounted on one end of the sleeve, and engaging connection means for engaging and connecting the stopper ring and the sleeve such that the two are relatively unmovable in the axial direction. In this embodiment, each setting spacer has a mounting portion attachable to and removable from the stopper ring and an engaging portion to engage with the aforesaid positioning surface. The engaging connection means comprises an annular groove formed in the inner circumferential portion of the stopper ring, a plurality of pin engaging holes formed in the sleeve, a plurality of headed pins which have each a pin portion to engage with the pin engaging hole and a head to engage with the annular groove of the stopper ring such that the head is relatively movable in the circumferential direction of the ring and relatively unmovable in the axial direction, and a plurality of head lead-in inlets which are formed on one end face of the stopper ring to open the aforesaid annular groove at a plurality of points in the circumferential direction and which permit the heads of the headed pins engaging with the pin engaging holes to be introduced into the aforesaid annular groove by relatively moving the headed pins in the axial direction of the ring.
In another preferred embodiment, the stationary seal unit has a cylindrical mounting case to be installed on the shaft seal casing, a stationary seal unit held inside the mounting case, and a circular positioning surface formed in the mounting case concentrically with the stationary seal unit. The rotary seal unit has a sleeve, that is, a thin wall cylinder which can be mounted around or removed from the rotary shaft without difficulty and which is placed concentrically in the stationary seal unit with part of the sleeve protruding from the mounting case, a rotary seal ring installed, opposed to the stationary seal ring, on the other end of the sleeve, a stopper ring which is inserted around one end of the sleeve, first set screws which are screwed into the stopper ring and can be tightened up on the outer circumferential surface of the sleeve, second set screws which are screwed into the stopper ring and can be tightened up on the circumferential surface of the rotary shaft portion through the sleeve. In that embodiment, each setting spacer has a mounting portion attachable to and removable from the stopper ring, an axial direction positioning portion thrust into and engaging with an engaging hole formed in the sleeve, and a radial direction positioning portion engaging with the positioning surface. On the other hand, the seal units include spring members to thrust and bring the two seal rings into contact with each other. The portion for positioning the setting spacer in the axial direction is pressed between the mounting case and the opposite face of the stopper ring by the thrusting force of the spring members, with the two seal rings properly pressed against and kept in contact with each other. The engaging holes of the sleeve are formed at positions where the axial direction positioning portions in such a pressed state engage with the holes.
In still another preferred embodiment, the mechanical seal comprises a stationary seal unit held in the mounting case movable in the axial direction, a rotary seal ring clamped, opposed to one end of the stationary seal ring, on the rotary shaft side and spring members to thrust the stationary seal ring against the rotary seal ring. In such an embodiment, an annular recession is formed on the outer circumferential portion at the other end of the stationary seal ring. A spring receptor made of an annular plate with part of it cut off is engaged with and clamped on that annular recession by its material elasticity. And the spring members are placed between the spring receptor and the opposite mounting case. There are formed engaging grooves at the other end of the stationary seal ring. With these engaging holes are engaged the drive pins fixed on the mounting case. The outer circumferential surface at the other end of the stationary seal ring is tapered, with the diameter gradually reduced from the annular recession.